Ultrasound flow measurement and particularly color flow mapping (CFM) systems provide a valuable tool for medical diagnosis. These techniques primarily exploit the Doppler effect which, despite its great success, results in two fundamental drawbacks: (1) the inability to measure nonaxial flow components and (2) the inability to measure high velocities at large depths. We propose to develop a system which (1) provides the capability for measuring the transverse components of flow velocity and (2) can measure very high velocities, both with high lateral resolution. The technique uses a newly developed multi-beam acoustic lens in which the separations between the acoustic foci are pre-determined by the lens design. The ultrasound signals are scattered from these foci are cross-correlated, resulting in flow velocity measurement. In Phase I this will be demonstrated by a suitable dual-beam acoustic lens using flow phantom. This will then pave the way for a 3-D velocity vector imaging system. During Phase II, we would like to develop a three-beam system and combine it with conventional Doppler for a complete 3-D flow velocity vector imaging system. We believe such a system will accurately detect flow disturbances arising from, for example, atherosclerotic lesions.